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Articles 1 - 15 of 15
Full-Text Articles in Life Sciences
Glutamine Synthetase Partitioning In Native And Introduced Salt Marsh Grasses, Eric L.G. Hazelton, Thomas J. Knight Phd, Theresa A. Theodose Phd
Glutamine Synthetase Partitioning In Native And Introduced Salt Marsh Grasses, Eric L.G. Hazelton, Thomas J. Knight Phd, Theresa A. Theodose Phd
Faculty Publications
Plants with higher glutamine synthetase (GS) activity in photosynthetic tissues than below-ground structures (high leaf:root [L:R] GS activity) show growth advantages over plants with a low L:R GS activity ratio. The benefits of a high L:R GS activity ratio are well documented in agricultural systems, but little is known about the ecology of GS partitioning in natural systems. To determine the ecological significance of GS partitioning, we measured above- and below-ground GS activity in Spartina grasses field-collected from a Maine salt marsh and others raised in a growth chamber from seed. The more stress-tolerant, faster growing S. alterniflora had a …
Latitudinal Differences In The Hibernation Characteristics Of Woodchucks (Marmota Monax), Stam M. Zervanos, Christine R. Maher Phd, Jerry A. Waldvogel, Gregory L. Florant
Latitudinal Differences In The Hibernation Characteristics Of Woodchucks (Marmota Monax), Stam M. Zervanos, Christine R. Maher Phd, Jerry A. Waldvogel, Gregory L. Florant
Faculty Publications
There is little information on the phenotypic flexibility of hibernation characteristics within species. To address this issue, we observed differences in hibernation characteristics of three free-ranging populations of woodchucks (Marmota monax) distributed along a latitudinal gradient from Maine to South Carolina. Data from free-ranging animals exhibited a direct relationship between latitude and length of the hibernation season. As expected, woodchucks in the northern latitudes hibernated longer than those in the southern latitudes. Also, the length of interbout arousals decreased with increase in latitude, whereas the length of torpor bouts and the number of arousals increased. Thus, we observed phenotypic plasticity …
Seal Bounties In Maine And Massachusetts, 1888 To 1962, Barbarai Lelli, David Harris Ph.D, Aboueissa Abouel-Makarim
Seal Bounties In Maine And Massachusetts, 1888 To 1962, Barbarai Lelli, David Harris Ph.D, Aboueissa Abouel-Makarim
Faculty Publications
Maine and Massachusetts paid bounties on seals during the 19th and 20th centuries. To determine the number of seals killed for bounty, we examined historical records of bounty claims, and used geographic information systems and multiple linear regression to find predictors of places where large numbers of bounties were paid. We found records of 24,831 bounties paid in Maine (1891-1945) and 15,690 in Massachusetts (1888-1962), Considering possible fraud, missing data, and seals struck and lost, this suggests that 72,284 to 135,498 seals were killed in the bounty hunt, probably enough to account for regional declines in seal populations. Larger numbers …
A Direct Role Of Jh In The Control Of Imaginal Disc Formation And Growth In Manduca, J. W. Truman, K. Hiruma, J. P. Allee, S.G.B. Macwhinnie, David Champlin Ph.D., L. M. Riddiford
A Direct Role Of Jh In The Control Of Imaginal Disc Formation And Growth In Manduca, J. W. Truman, K. Hiruma, J. P. Allee, S.G.B. Macwhinnie, David Champlin Ph.D., L. M. Riddiford
Faculty Publications
No abstract provided.
Gis-Based Analysis Of Ice-Breeding Seal Strandings In The Gulf Of Maine, David Harris Ph.D., Sat Gupta
Gis-Based Analysis Of Ice-Breeding Seal Strandings In The Gulf Of Maine, David Harris Ph.D., Sat Gupta
Faculty Publications
Phoca groenlandica (harp seals) and Cystophora cristata (hooded seals), two species of ice-breeding seals, are being sighted more frequently onshore in the Gulf of Maine since 1990, but little is known about their behavior in this ecosystem. We obtained records of 904 ice-breeding seal stranding locations in the Gulf of Maine between 1996 and 2002 from NOAA Fisheries and used a geographic information system (GIS) to conduct group-wise comparisons by species (using non-parametric techniques), and to determine the predictors of high seal-stranding density (using ordinal logistic regression analysis). Compared to harp seals, hooded seals stranded closer to deep water, farther …
Ecotypic Variation In Phosphorus Acquisition Mechanisms Within Marine Picocyanobacteria, Lisa Moore Phd, M. Ostrowski, D. J. Scanlan, K. Feren, T. Sweetsir
Ecotypic Variation In Phosphorus Acquisition Mechanisms Within Marine Picocyanobacteria, Lisa Moore Phd, M. Ostrowski, D. J. Scanlan, K. Feren, T. Sweetsir
Faculty Publications
Prochlorococcus and Synechococcus are major prokaryotic primary producers in the oligotrophic oceans that may be affected by the climate-related increases in nitrogen fixation and subsequent phosphorus (P) limitation in some parts of the oceans. Evidence that Prochlorococcus populations in the North Pacific subtropical gyre (NPSG) have increased over the past decades, possibly due to having a competitive advantage under conditions of P limitation, suggests aspects of their Pphysiology that are important for dictating their in situ success. Here, we compared the physiology of P acquisition and response to P stress (indicated by alkaline phosphatase activity, APA) among isolates of Prochlorococcus …
Constraints On Adaptive Evolution: The Functional Trade-Off Between Reproduction And Fast-Start Swimming Performance In The Trinidadian Guppy (Poecilia Reticulata), Cameron K. Ghalambor, David N. Reznick, Jeffrey A. Walker Phd
Constraints On Adaptive Evolution: The Functional Trade-Off Between Reproduction And Fast-Start Swimming Performance In The Trinidadian Guppy (Poecilia Reticulata), Cameron K. Ghalambor, David N. Reznick, Jeffrey A. Walker Phd
Faculty Publications
The empirical study of natural selection reveals that adaptations often involve trade-offs between competing functions. Because natural selection acts on whole organisms rather than isolated traits, adaptive evolution may be constrained by the interaction between traits that are functionally integrated. Yet, few attempts have been made to characterize how and when such constraints are manifested or whether they limit the adaptive divergence of populations. Here we examine the consequences of adaptive life-history evolution on locomotor performance in the live-bearing guppy. In response to increased predation from piscivorous fish, Trinidadian guppies evolve an increased allocation of resources toward reproduction. These populations …
Dynamics Of Pectoral Fin Rowing In A Fish With An Extreme Rowing Stroke: The Threespine Stickleback (Gasterosteus Aculeatus), Jeffrey A. Walker Phd
Dynamics Of Pectoral Fin Rowing In A Fish With An Extreme Rowing Stroke: The Threespine Stickleback (Gasterosteus Aculeatus), Jeffrey A. Walker Phd
Faculty Publications
The dynamics of pectoral fin rowing in the threespine stickleback are investigated by measuring the instantaneous force balance on freely swimming fish throughout the stroke cycle and comparing the measured forces with fin motions and an unsteady, blade-element model of pectoral fin propulsion. Both measured and modeled forces suggest that attached vortex and circulatory forces and not inertial (added mass) forces dominate the force balance. Peak forces occur at midstrokes. There is no evidence for large force peaks at the stroke transitions due to either rapid fin rotation (supination) or rapid fin closure against the body. The energetics of pectoral …
Nitric Oxide Mediates Seasonal Muscle Potentiation In Clam Gills, Louis F. Gainey Jr., Michael J. Greenberg
Nitric Oxide Mediates Seasonal Muscle Potentiation In Clam Gills, Louis F. Gainey Jr., Michael J. Greenberg
Faculty Publications
The physiology and timing of gill muscle potentiation were explored in the clam Mercenaria mercenaria. When isolated demibranchs were exposed twice (with an intervening wash) to the same concentration of 5-hydroxytryptamine, the second contraction was larger than the first. This potentiation was seasonal: it was present from November through June, and absent from July through October. Potentiation was not affected by the geographic origin of the clams, nor by their acclimation temperature. Potentiation was inhibited by the nitric oxide synthase (NOS) inhibitor L-NAME and mimicked by the nitric oxide (NO) donor DEANO. During the season of potentiation, immunoreactive NOS appeared …
Long-Term Observations Of A Harbor Seal Haul-Out Site In A Protected Cove In Casco Bay, Gulf Of Maine, David Harris Phd, Barbarai Lelli, Sat Gupta
Long-Term Observations Of A Harbor Seal Haul-Out Site In A Protected Cove In Casco Bay, Gulf Of Maine, David Harris Phd, Barbarai Lelli, Sat Gupta
Faculty Publications
We counted the numbers of seals hauled out at low tide on two near-shore ledges in a protected cove in Casco Bay, Gulf of Maine a minimum of 12 times per month, for four years starting in August 1997. The highest mean monthly counts were in August (molting season) and the lowest in either January or February. Counts during pupping season (May and June) were lower than during April or July. As no mother-pup pairs were observed, these ledges are molting but not pupping ledges. Time-series analysis revealed no overall trend in the number of seals present. but did show …
Rotational Lift: Something Different Or More Of The Same?, Jeffrey A. Walker Phd
Rotational Lift: Something Different Or More Of The Same?, Jeffrey A. Walker Phd
Faculty Publications
This paper addresses the question, do the rotational forces in the hovering fruit fly Drosophila melanogaster reflect something different (the Magnus effect) or more of the same (circulatory-and-attached-vortex force)? The results of an unsteady blade-element model using empirically derived force coefficients from translating (root-oscillating) wings are compared with recent results derived from both the measured forces on a dynamically scaled Drosophila wing and the computational fluid dynamic (CFD)-modeled forces on a virtual Drosophila wing. The behavior of the forces in all three models during wing rotation supports the hypothesis that rotational lift is not a novel aerodynamic mechanism but is …
Fluid Dynamics Of Flapping Aquatic Flight In The Bird Wrasse: Three-Dimensional Unsteady Computations With Fin Deformation, Ravi Ramamurti, William C. Sandberg, Rainald Lӧhner, Jeffrey A. Walker Phd, Mark W. Westneat
Fluid Dynamics Of Flapping Aquatic Flight In The Bird Wrasse: Three-Dimensional Unsteady Computations With Fin Deformation, Ravi Ramamurti, William C. Sandberg, Rainald Lӧhner, Jeffrey A. Walker Phd, Mark W. Westneat
Faculty Publications
Many fishes that swim with the paired pectoral fins use fin-stroke parameters that produce thrust force from lift in a mechanism of underwater flight. These locomotor mechanisms are of interest to behavioral biologists, biomechanics researchers and engineers. In the. present study, we performed the first three-dimensional unsteady computations of fish swimming with oscillating and deforming fins. The objective of these computations was to investigate the fluid dynamics of force production associated with the flapping aquatic flight of the bird wrasse Gomphosus varius. For this computational work, we used the geometry of the wrasse and its pectoral fin, and previously measured …
Performance Limits Of Labriform Propulsion And Correlates With Fin Shape And Motion, Jeffrey A. Walker Phd, Mark W. Westneat
Performance Limits Of Labriform Propulsion And Correlates With Fin Shape And Motion, Jeffrey A. Walker Phd, Mark W. Westneat
Faculty Publications
Labriform locomotion, which is powered by oscillating the paired pectoral fins, varies along a continuum from rowing the fins back and forth to flapping the fins up and down. It has generally been assumed (i) that flapping is more mechanically efficient than rowing, a hypothesis confirmed by a recent simulation experiment, and (ii) that flapping should be associated with wing-shaped fins while rowing should be associated with paddle-shaped fins, To determine whether these hypotheses and the results of the simulation experiment are consistent with natural variation, we compared the steady swimming performance (critical swimming speed) of four species of labrid …
Does A Rigid Body Limit Maneuverability?, Jeffrey A. Walker Phd
Does A Rigid Body Limit Maneuverability?, Jeffrey A. Walker Phd
Faculty Publications
Whether a rigid body limits maneuverability depends on how maneuverability is defined. By the current definition, the minimum radius of the turn, a rigid-bodied, spotted boxfish Ostracion meleagris approaches maximum maneuverability, i.e. it can spin around with minimum turning radii near zero. The radius of the minimum space required to turn is an alternative measure of maneuverability. By this definition, O. meleagris is not very maneuverable. The observed space required by O. meleagris to turn is slightly greater than its theoretical minimum but much greater than that of highly flexible fish. Agility, the rate of turning, is related to maneuverability. …
Teaching The Ethics Of Biology, David Harris Phd, Carol K. Johansen
Teaching The Ethics Of Biology, David Harris Phd, Carol K. Johansen
Faculty Publications
Discusses the basic principles of ethics and ethical decision making as applied to biology. Ethical issues associated with biology; Theoretical basis of ethical decision-making; Models of ethical decision-making; Social implications of scientific experimentation and discovery.